abstracts: geology 601 



dice to any valley interest except navigation. The important interest 

 which now dictates that debris should be controlled is that of the com- 

 merce which traverses the Golden Gate. Possibilities for resumption 

 of mining on a large scale, with storage of debris, lie in cooperation with 

 irrigation and electric-power development for the control of Sierra 

 streams. R. W. Stone. 



GEOLOGY. — Geologic history indicated by the fossiliferous deposits of 

 the Wilcox group (Eocene) at Meridian, Mississippi. Edward 

 Wilber Berry. U. S. Geological Survey Professional Paper 

 108-E. Pp. 12, with 2 plates and 2 figures. 1917. 

 This paper discusses briefly new and important additions to the 

 flora of the Wilcox group and new evidence of the unconformity be- 

 tween the Wilcox and the Claiborne groups. 



The conclusion seems justified that the upper Wilcox was a time 

 during which the open sea became gradually smaller as the strand line 

 moved southward, and that there was an interval of emergence be- 

 tween the deposition of the Wilcox and that of the Claiborne group, 

 an interval whose considerable length is indicated by the great con- 

 trasts between the terrestrial floras and the marine faunas of the Wilcox 

 and the Claiborne. 



The two new species described are of especial interest in that the 

 Nelumbo adds an entirely new type to the Wilcox flora, and the second 

 adds a new cycad (Zamia), represented by fronds, the only known cycad 

 from the American Tertiary except a single piece of a pinnule of another 

 species of Zamia from the Wilcox. R. W. Stone. 



GEOLOGY. — A fossil flora from the Frontier formation of southwestern 

 Wyoming. F. H. Knowlton. U. S. Geological Survey Pro- 

 fessional Paper 108-F. Pp. 35, with 13 plates. 1917. 



This paper deals with a small but important fossil flora, now known 

 to be of Colorado age, from the vicinity of Cumberland, Lincoln County, 

 Wyoming. Although small in number of species, this flora offers in- 

 formation bearing on the physical and climatic conditions that pre- 

 vailed in this region during early Upper Cretaceous time. It has also 

 a possibly important biologic bearing, for it shows the presence of 

 certain plant types that are now living in Polynesia. The plants de- 

 scribed occur in what is now known as the Frontier formation. 



The known flora from the Frontier formation near Cumberland em- 

 braces 25 forms, of which 7 are ferns, 1 an Equisetum, 1 a monocotyle- 



